Manual reset thermostatic switch in protective systems



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v. s VAUGHAN HANUAL RESET THERMOSTATIC SWITGE! IN PROTECTIVE SYSTEEBSFiled June 28, 1943:

FIG 2.

Patented Sept. 2, 1947 UNITED STATES ,iitstt MANUAL RESET THERMOSTATICSWITCH IN PROTECTIVE SYSTEMS Victor G. Vaughan, Attleboro, Mass,assigncr to Metals & Controls Corporation,

Attleboro,

11 Claims. 1

This invention relates to electrical protective apparatus, and withregard to certain more we ciflc features, to thermostatically controlledprotective means for electric motors and the like.

Among the several objects of the invention may be noted the provision ofmechanically and elec trically simple protection apparatus forelectrical energy translating devices (for example a motor ortransformer) which allows manual reset means to be located at a distancefrom the protected apparatus while only small and compact parts aremounted on the casing of the protected apparatus. Other objects will bein part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawing, in which are illustrated several of variouspossible embodiments of the invention,

Fig-l is a wiring diagram showing one form of the invention; and,

Fig. 2 is a wiring diagram showing a second form.

Similar reference characters indicate some sponding parts throughout theseveral views of the drawing.

Referring now more particularly to Fig. 1, there is shown at M a motorwhich is to be protected against overheating due either to overload orhigh ambient temperature. The circuit supplying the motor is shown at C.At numeral I is shown an automatic reset thermostatic protectiveassembly which it is intended shall be small enough to be mounted uponthe motor casing, or at least be in the close vicinity of the motor soas to be responsive to ambient temperature conditions around the motor.

At 3 is shown a manual reset thermostatic assembly intended to beremotely located with respect to the motor.

Assembly I has main contacts 5 and 'l. Contact 5 is connected with thecircuit C by wire Fl. Contact l is connected with a third contact H byway of a resistance heater l3 which is located closely adjacent to anautomatic reset thermostatic element i5. The mechanical details of thethermostatic element I5 are shown in United States Patent 2,199,387.Thus i5 is a. bimetallic snap-acting thermostatic disc which upontemperature rise from normal temperature conditions snaps to an oppositecurvature, thereby removing is reduced to normal.

' this time forms the contacts ii and it carried thereby from the tests5 and i. Upon reduction in temper the disc l5 snaps baclc to thecurvature shown to reclose contacts 5, it and l, ll. it is classified asan automatic reset thermostat.

The assembly ii is composed oi stationary con tacts 2E and 23 in a lineand terminals and 29 between which is a resistance heater The contacts2i and 29 are in a circuit; 33 which connects across the contacts 5 and"i in assembly 6.

A thermostatic disc of the snap-acting type carries movable contacts iiiand St for opening and closing the contacts and in line The thermostaticdisc 35 is oi. the so-cailed manual reset type, which i'ec'ioses only bymanual operation of a reset button. i That is t s if the disc snaps toopen position ups ing, it will remain in that position until manually,even though the temperature s n The details of a typical manual resetthermostat are disclosed in United States Patent 2,199,388.

Operation is as follows:

When the motor M is energized over the line C, current flows through themotor, line it, con tacts 5, iii, thermostatic disc 55, contactsresistance l3, line 2%, contacts disc contacts 31', 2| and back to theline C. No substantial current at this time flows through the resistance3!, since there is very little potential. applied across thisresistance, the resistance disc l5 being low.

If the motor becomes electrically overloaded, or overheated, thethermostatic disc it will re spond by snapping to reverse curvature andre move contacts ii, iii from contacts 5, i. i3 accelerates the heatingof the disc l5. With open, current will thus be forced to flow from theline C through terminal 2], heater 3i, terminal 29, line 33, contact i,heater it, terminal ii. line 25, returning to the line C through thecontacts 23, disc 35. contacts ill and iii, back to the line C. Heatingof the disc 35 by the adjacent heater 3i causes the disc to'open. theline which at is ooiy connection closing the circuit C. Once disc snapsto open posi-- tion, it will remain there until reset by manualoperation on the button iii. Thus even though disc it may reclose, amanual reclosure at is necessary.

From the above it will be seen that the of operation of the automaticreset disc open and shut the circuit across the re thus acting as arelay. Aite operated to break the circuit, :.l

3 that the automatic disc ll rec l oses the contacts Ii, l9 and I, I!because then the circuit C is in any event broken at contacts 2| and 2!.

Advantages of the invention are that the relay assembly I may be madesmall and sensitive and mounted on or near the motor while the assemblyI may be made larger in its remote location.

At Fig. 2 is shown a form of the invention arranged so that theresistance l3 in the assembly I, when It is open, is not (as in Fig. 1)in series with the resistance II. To this end, the connection 33 andcontact 29 are eliminated and the resistance II is connected betweenterminal 21 and contact 23 of the reset switch I. In this case, overloadcurrent first passes through connection 8, disc ll, heating resistanceIt, line 25, disc 35 and back to the line C. The heater It causes discII to snap open initially, whereupon the circuit traces from line C toterminal 21 in assembly I, heater resistance 3|, disc 35 and back to theline C. The heater 3| then causes opening of the thermostatic element I5which completely breaks tb motor circuit. This allows the automaticreset thermostat I to return to position prior to resetting the resetthermostat 8, without placing the motor back in the line.

It will be understood that the invention will provide protection forother translating or similar apparatus equivalent to the motor shown.

In view of the above, it will be seen that the several objects oi theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. Electrical protective means in a supply circuit, comprising a manualreset thermostat, an automatic reset thermostat, a heater elementassociated with each of said thermostats, a circuit placing the manualreset thermostat in series with the heater element of the automaticreset thermostat, means connecting the automatic reset thermostat sothat when cold it shunts the heater element of the manual resetthermostat and when hot opens said shunt, and circuit means which placessaid heater element of the manual reset thermostat in series connectionwith said manual reset thermostat when said shunt is op n.

2. Electrical protective means in a supply circuit comprising a manualreset thermostat, an automatic reset thermostat, a heater elementassociated with each of said thermostats, a circuit placing the manualreset thermostat in series with the heater element of the automaticreset thermostat, means connecting the automatic reset thermostat, sothat when cold it shunts the heater element of the manual resetthermostat and when hot opens said shunt, circuit means which placessaid heater element or the manual reset thermostat in series connectionwith said manual reset thermostat when said shunt is open, saidlast-named circuit means being arranged to connect both or said heaterelements in series when said shunt is open.

3. Electrical protective means in a supply circuit comprising a manualreset thermostat, an automatic reset thermostat, a heater elementassociated with each of said thermostats, a circuit placing the manualreset thermostat in series with the heater element or the automaticreset thermostat, means connecting the automatic reset thermostat sothat when cold it shunts the heater element of the manual resetthermostat and when hot opens said shunt, circuit means which placessaid heater element of the manual reset thermostat in series connectionwith said manual reset thermostat when said shunt is opened, saidlastnamed circuit means being arranged to cut out of circuit the heaterelement of the automatic reset thermostat when said shunt is open.

4. In apparatus of the class described, an automatic reset thermostatassembly and a manual reset thermostat assembly, a thermostatic switchmember and a heater in the automatic assembly and a thermostatic switchand a heater in the manual assembly, the thermostatic switch of theautomatic assembly, its heater and the thermostatic switch of the manualassembly being normall in series, the thermostatic switch of theautomatic assembly when closed shunting the heater of the manualassembly.

5. In apparatus of the class described, an automatic reset thermostatassembly and a manual reset thermostat assembly, a thermostatic switchmember and a heater in the automatic assembly and a thermostatic switchand a heater in the manual assembly, the thermostaticswitch oi theautomatic assembly, its heater and the thermostatic switch of the manualassembly being normally in series, the thermostatic switch of theautomatic assembly when closed and its heater shunting the heater or themanual assembly,

6. In apparatus of the class described, an automatic reset thermostatassembly and a manual reset thermostat assembly, a thermostatic switchmember and a heater in the automatic assembly and a thermostatic switchand a heater in the manual assembly, the thermostatic switch of theautomatic assembly, its heater and the thermostatic switch or the manualassembl being normally in series, the thermostatic switch of theautomatic assembly when closed shunting the heater of the manualassembly and said heaters being in series connection when the automaticreset thermostat is open.

7. In apparatus of the class described, an automatic reset thermostatassembly and a manual reset thermostat assembly, a thermostatic switchmember and a heater in the automatic assembly and a thermostatic switchand a heater in the manual assembly, the thermostatic switch oi theautomatic assembly, its heater and the thermostatic switch of the manualassembly being normally in series, the thermostatic switch of theautomatic assembly when closed and its heater shunting the heater of themanual assembly and when the automatic reset thermostat is open saidheater in the manual assembly being in series connection with the manualreset thermostat and the heater in the automatic assembly beingdisconnected.

8. In apparatus of the class described, an automatic reset thermostaticswitch and a heater therefor, a manual reset thermostatic switch and aheater therefor, the automatic thermostatic switch, its heater and themanual thermostatic switch being normally in series, the automaticthermostatic switch when automatically closed shunting the heater oi themanual thermostatic switch, and means forming a series connectionbetween the two heaters when the automatic thermostatic switch is open.

9. In apparatus or the class described, an automatic reset thermostaticswitch and a heater therefor, a manual reset thermostatic switch and aheater therefor, the automatic thermostatic switch, its heater and themanual thermostatic cuit comprising a manual reset thermostat, an-

automatic reset thermostat, a heater element associated with each ofsaid thermostats, a circuit placing the manual reset thermostat inseries with the heater element of the automatic reset thermostat andwith the automatic reset thermostat, means connecting the automaticreset thermostat so that when cold it shunts the heater element of themanual reset thermostat and when hot opens said shunt, and circuit meanswhich places said heater element oi. the manual reset thermostat inseries connection with said manual reset thermostat when said shunt isopen. K

11. Electrical protective means in a supply circuit comprising a manualreset thermostat, an automatic reset thermostat, a heater elementassociated with each oi said thermostats, a circuit placing the manualreset thermostat in series with the heater element of the automaticreset thermostat and with the automatic reset thermostat, meansconnectinz the automatic reset thermostat so that when cold it and itsheater shunt the heater element of the manual reset thermostat and whenhot it opens said shunt, and circuit means which places said heaterelement of the manual reset thermostat in series connection with saidmanual reset thermostat when said shunt is open.

VICTOR G. VAUGHAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PA'I'ENTS Weeks Jan. 23, 1945

